Record size of scroller that user scrolls

third_party/WebKit/Source/core/input/EventHandlerTest.cpp

Index: third_party/WebKit/Source/core/input/EventHandlerTest.cpp
diff --git a/third_party/WebKit/Source/core/input/EventHandlerTest.cpp b/third_party/WebKit/Source/core/input/EventHandlerTest.cpp
index fd1d83710e613c6562a55c148db4514b11f6f1ee..a6d2ca486937cc3e85ceb10b12da2c95b47c2ae4 100644
--- a/third_party/WebKit/Source/core/input/EventHandlerTest.cpp
+++ b/third_party/WebKit/Source/core/input/EventHandlerTest.cpp
@@ -20,6 +20,7 @@
 #include "core/paint/PaintLayerScrollableArea.h"
 #include "core/testing/DummyPageHolder.h"
 #include "platform/scroll/MainThreadScrollingReason.h"
+#include "platform/scroll/ScrollerSizeMetrics.h"
 #include "platform/testing/HistogramTester.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -52,8 +53,8 @@ class EventHandlerTest : public ::testing::Test {
   FrameSelection& Selection() const {
     return GetDocument().GetFrame()->Selection();
   }
-
   void SetHtmlInnerHTML(const char* html_content);
+  void Scroll(Element*, const WebGestureDevice);
 
  protected:
   std::unique_ptr<DummyPageHolder> dummy_page_holder_;
@@ -62,43 +63,7 @@ class EventHandlerTest : public ::testing::Test {
 class NonCompositedMainThreadScrollingReasonRecordTest
     : public EventHandlerTest {
  protected:
-  class ScrollBeginEventBuilder : public WebGestureEvent {
-   public:
-    ScrollBeginEventBuilder(IntPoint position,
-                            FloatPoint delta,
-                            WebGestureDevice device)
-        : WebGestureEvent() {
-      type_ = WebInputEvent::kGestureScrollBegin;
-      x = global_x = position.X();
-      y = global_y = position.Y();
-      data.scroll_begin.delta_y_hint = delta.Y();
-      source_device = device;
-      frame_scale_ = 1;
-    }
-  };
-
-  class ScrollUpdateEventBuilder : public WebGestureEvent {
-   public:
-    ScrollUpdateEventBuilder() : WebGestureEvent() {
-      type_ = WebInputEvent::kGestureScrollUpdate;
-      data.scroll_update.delta_x = 0.0f;
-      data.scroll_update.delta_y = 1.0f;
-      data.scroll_update.velocity_x = 0;
-      data.scroll_update.velocity_y = 1;
-      frame_scale_ = 1;
-    }
-  };
-
-  class ScrollEndEventBuilder : public WebGestureEvent {
-   public:
-    ScrollEndEventBuilder() : WebGestureEvent() {
-      type_ = WebInputEvent::kGestureScrollEnd;
-      frame_scale_ = 1;
-    }
-  };
-
   int GetBucketIndex(uint32_t reason);
-  void Scroll(Element*, const WebGestureDevice);
 };
 
 class TapEventBuilder : public WebGestureEvent {
@@ -146,6 +111,41 @@ class MousePressEventBuilder : public WebMouseEvent {
   }
 };
 
+class ScrollBeginEventBuilder : public WebGestureEvent {
+ public:
+  ScrollBeginEventBuilder(IntPoint position,
+                          FloatPoint delta,
+                          WebGestureDevice device)
+      : WebGestureEvent() {
+    type_ = WebInputEvent::kGestureScrollBegin;
+    x = global_x = position.X();
+    y = global_y = position.Y();
+    data.scroll_begin.delta_y_hint = delta.Y();
+    source_device = device;
+    frame_scale_ = 1;
+  }
+};
+
+class ScrollUpdateEventBuilder : public WebGestureEvent {
+ public:
+  ScrollUpdateEventBuilder() : WebGestureEvent() {
+    type_ = WebInputEvent::kGestureScrollUpdate;
+    data.scroll_update.delta_x = 0.0f;
+    data.scroll_update.delta_y = 1.0f;
+    data.scroll_update.velocity_x = 0;
+    data.scroll_update.velocity_y = 1;
+    frame_scale_ = 1;
+  }
+};
+
+class ScrollEndEventBuilder : public WebGestureEvent {
+ public:
+  ScrollEndEventBuilder() : WebGestureEvent() {
+    type_ = WebInputEvent::kGestureScrollEnd;
+    frame_scale_ = 1;
+  }
+};
+
 void EventHandlerTest::SetUp() {
   dummy_page_holder_ = DummyPageHolder::Create(IntSize(300, 400));
 }
@@ -166,9 +166,7 @@ int NonCompositedMainThreadScrollingReasonRecordTest::GetBucketIndex(
   return index;
 }
 
-void NonCompositedMainThreadScrollingReasonRecordTest::Scroll(
-    Element* element,
-    const WebGestureDevice device) {
+void EventHandlerTest::Scroll(Element* element, const WebGestureDevice device) {
   DCHECK(element);
   DCHECK(element->getBoundingClientRect());
   ClientRect* rect = element->getBoundingClientRect();
@@ -181,6 +179,7 @@ void NonCompositedMainThreadScrollingReasonRecordTest::Scroll(
   GetDocument().GetFrame()->GetEventHandler().HandleGestureEvent(scroll_begin);
   GetDocument().GetFrame()->GetEventHandler().HandleGestureEvent(scroll_update);
   GetDocument().GetFrame()->GetEventHandler().HandleGestureEvent(scroll_end);
+  ASSERT_GT(scroll_update.DeltaYInRootFrame(), 0);
 }
 
 TEST_F(EventHandlerTest, dragSelectionAfterScroll) {
@@ -581,6 +580,51 @@ TEST_F(EventHandlerTest, dragEndInNewDrag) {
   // This test passes if it doesn't crash.
 }
 
+TEST_F(EventHandlerTest,
+       ScrollerSizeOfMainThreadScrollingHistogramRecordingTest) {
+  SetHtmlInnerHTML(
+      "<style>"

[bokan, 2017/04/20 19:27:58]

Please add <!DOCTYPE html>

[yigu, 2017/04/20 20:22:35]

Done.

+      " .container { width: 200px; height: 200px; overflow: scroll; }"

[bokan, 2017/04/20 19:27:58]

I think the intent is to have the container scrollable, right? Right now it
isn't since the box is only 100x100.

[yigu, 2017/04/20 20:22:35]

I think the container itself doesn't need to be scrollable.

+      " .box { width: 100px; height: 100px; overflow: scroll; }"
+      " .fixed { position: fixed; }"
+      " .spacer { height: 1000px;} body { height: 2000px; }"

[bokan, 2017/04/20 19:27:58]

Place the body style on a new line (I almost missed it).

[yigu, 2017/04/20 20:22:35]

Done.

+      "</style>"
+      "<div class='container'>"
+      " <div id='box' class='box'>"
+      "  <div id='content' class='spacer'></div>"
+      " </div>"
+      "</div>"
+      "<img src='image.png' class='fixed'></img>");

[bokan, 2017/04/20 19:27:58]

Why do you need a image?

[yigu, 2017/04/20 20:22:35]

Without a fix positioned image, the main scroller should be scrolled on the
compositor. It doesn't affect the test here because we manually call
ScrollBegin. Just remove it to be clear.

+
+  Element* box = GetDocument().getElementById("box");
+  HistogramTester histogram_tester;
+
+  // Test wheel scroll on the box.
+  Scroll(box, kWebGestureDeviceTouchpad);
+  histogram_tester.ExpectBucketCount("Event.Scroll.ScrollerSize.OnScroll_Wheel",
+                                     10000, 1);
+  // Only the first scrollable area is recorded.
+  histogram_tester.ExpectBucketCount("Event.Scroll.ScrollerSize.OnScroll_Wheel",
+                                     40000, 0);
+  histogram_tester.ExpectTotalCount("Event.Scroll.ScrollerSize.OnScroll_Wheel",

[bokan, 2017/04/20 19:27:58]

Please also add after this

1) programmatically fully scroll "box"
2) scroll over "box"
3) check that we do record 40000 and not 10000

[bokan, 2017/04/20 20:07:31]

Never mind, ScrollBegin will always hit the top scroller so this doesn't work as
I expected.

+                                    1);
+
+  // Test touch scroll.
+  Scroll(box, kWebGestureDeviceTouchscreen);
+  histogram_tester.ExpectBucketCount("Event.Scroll.ScrollerSize.OnScroll_Touch",
+                                     10000, 1);
+  histogram_tester.ExpectTotalCount("Event.Scroll.ScrollerSize.OnScroll_Touch",
+                                    1);
+
+  // Scrolling root layer doesn't add to count.
+  Element* body = GetDocument().body();
+  Scroll(body, kWebGestureDeviceTouchscreen);

[bokan, 2017/04/20 19:27:58]

This works but is fragile. The way Scroll() works is it sends a scroll to the
middle of the given element. Because body is 2000px tall, the coordinate of the
scroll gesture is way off screen. This is unrealistic. You can fix this by
either:

- Rearranging the example elements so that the middle of body is within the
frame but not overlapped by other elements.
- Adding a "bodyScrollTarget" div (child of body) that doesn't have scrolling
itself and is used solely to target a specific part of the page
- Let Scroll take a specific coordinate

I think the second is the most clear to the reader.

[yigu, 2017/04/20 20:22:35]

Done.

+  histogram_tester.ExpectBucketCount("Event.Scroll.ScrollerSize.OnScroll_Touch",
+                                     kScrollerSizeLargestBucket, 0);
+  histogram_tester.ExpectTotalCount("Event.Scroll.ScrollerSize.OnScroll_Touch",
+                                    1);
+}
+
 class TooltipCapturingChromeClient : public EmptyChromeClient {
  public:
   TooltipCapturingChromeClient() {}